Why you should NEVER hit the snooze button on your alarm clock - and always get 8 hours of sleep!

• e-mail

Sleep: I’m in love with it and everything it does. And knowing what it does is why I give myself a non-negotiable eight hour sleep opportunity each night. Yes, eight hours.

As a neuroscientist and director of the University of California’s Centre for Human Sleep Science, I know most mainstream research agrees that eight hours of total sleep is the proper healthy amount for an average adult.

Tragically in the UK, however, 39 per cent of adults report sleeping for fewer than seven.

Routinely sleeping less than six or seven hours a night is linked to suicide and numerous health conditions, including Alzheimer’s, anxiety, depression, stroke and chronic pain — and to damage to every physiological system of the body, leading to cancer, diabetes, heart attacks, infertility and obesity.

Meanwhile proper sleep is beneficial for us in myriad ways, nurturing our memory and learning and boosting our immune defences, physical fitness and mental health.

In fact, sleep is the single most effective thing we can do for our health, wealth and well-being — even before diet or exercise.

Based on 20 years of research and findings from over 100 papers produced in my sleep centre, here I explain why we neglect sleep at our peril and how we can sleep better . . .

DON’T FALL INTO THE DECAF COFFEE TRAP

A key role in our process of falling asleep is played by a chemical called adenosine, which slowly builds up in the brain during our waking hours. Using a clever dual-action effect, high concentrations of adenosine turn down the wake-promoting regions in the brain and turn up the dial on the sleep-inducing regions.

When concentrations of adenosine peak, an irresistible urge for slumber will take hold. For most people, this happens after 12 to 16 hours awake.

You can mute the sleep signal of adenosine with caffeine. It works by occupying adenosine welcome sites — or ‘receptors’ — in the brain and effectively inactivating them.

Levels of caffeine peak approximately 30 minutes after you drink it. The problem is that it persists. In pharmacology, we use the term ‘half-life’ when discussing a drug’s efficacy, which refers to the time it takes for the body to remove 50 per cent of a drug’s concentration.

Be careful: Routinely sleeping less than six or seven hours a night is linked to suicide and numerous health conditions, experts say

Caffeine has a half-life of five to seven hours. So if you have a cup of coffee after your evening dinner, at around 7.30pm, then by 1.30am, 50 per cent of that caffeine may still be circulating in your brain. But half a shot of caffeine is still powerful.

Caffeine is removed from your system by an enzyme in the liver called cytochrome P450 1A2. Based largely on genetics, some people have a more efficient version of this enzyme, allowing the liver to clear caffeine rapidly from the bloodstream. These rare individuals can drink an espresso with dinner and fall fast asleep at midnight.

But as we age, it takes longer to remove caffeine, and we become more sensitive to its sleep-disrupting influence.

And note that ‘decaffeinated’ does not mean non-caffeinated. One cup of decaf usually contains up to a third of the dose of a regular cup of coffee. That means three to four cups in the evening are just as damaging to your sleep as one cup of regular coffee.

BEWARE THE SNOOZE BUTTON

When we are artificially wrenched from sleep by an alarm clock, a burst of activity from the fight-or-flight branch of the nervous system causes a spike in blood pressure and a shock acceleration in heart rate, according to research in the journal Industrial Health in 2005.

But an even greater danger lurks within the alarm clock: the snooze button. If alarming your heart, quite literally, were not bad enough, using the snooze feature means you will repeatedly inflict that cardiovascular assault again and again within a short span of time.

Repeating this at least five days a week in your working life, can cause multiplicative abuse to your heart and nervous system.

If you use an alarm clock, do away with the snooze function and get in the habit of waking up once to spare your heart the repeated shock.

MYTH OF THE POWER-NAP

Modern humans are not sleeping the way nature intended. Our ancient forebears evolved a biological way of sleeping which is still practised in cultures untouched by electricity, such as the Gabra hunter-gatherer tribe in northern Kenya.

Their way of life has changed little over thousands of years. They commonly sleep in a 'biphasic' pattern, where they have about seven hours of sleep at night, followed by a 30 to 60-minute nap in the afternoon. 

But in studies that I and others have performed, naps cannot salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning or decision making.

Also, naps are not recommended for those who have difficulties falling or staying asleep at night, since daytime naps can take the edge off your nighttime sleepiness. 

Are you getting enough? Sleep is the single most effective thing we can do for our health, wealth and well-being — even before diet or exercise

In fact, all humans, irrespective of culture or geographical location, have a genetically hardwired dip in alertness — in other words, they are programmed for a nap — in the mid-afternoon. Observe any post-lunch meeting around a boardroom table and this will become clear.

Having a daily siesta still exists in South America and Mediterranean Europe. But the habit is disappearing, causing deadly consequences.

In Greece, for example, siestas have largely disappeared since the millennium.

Harvard University researchers have now studied the effects of this radical change in more than 23,000 Greek adults. Those that abandoned regular siestas went on to suffer a 37 per cent increased risk of death from heart disease across the six-year period, compared with those who maintained regular daytime naps.

Working men’s overall mortality risk from no longer napping increased by more than 60 per cent. The fact is, when we stop the innate practice of biphasic sleep, our lives are shortened.

In small Greek enclaves where siestas remain intact, such as the island of Ikaria, men are nearly four times as likely to reach the age of 90 as American males. These have sometimes been described as ‘the places where people forget to die’. From a prescription written long ago in our ancestral genes, natural biphasic sleep and a healthy diet appear to be the keys to a long-sustained life.

That is not to say, however, that naps can make up for lost or poor overnight sleep. The myth of the all-curing 20-minute ‘power-nap’ has become popularised over the past three decades in response to the sleep-depriving pressures of modern working life.

Power-naps may momentarily increase basic concentration in people who are sleep-deprived. But in studies that I and others have performed, naps cannot salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning or decision making. 

SLEEP KILLS OFF CANCER

Natural killer cells are an elite squad in your immune system. They identify dangerous foreign elements and eliminate them. One entity they target are cancerous cells.

Natural killer cells will effectively punch a hole in their outer surface and inject a protein to destroy the malignancy. But if your sleep is poor, they lose their effectiveness.

Professor Michael Irwin, a sleep scientist at the University of California, Los Angeles, has performed landmark studies revealing just how quickly and comprehensively a brief dose of short sleep can affect cancer-fighting immune cells.

Too many to mention! Lack of sleep causes Alzheimer’s, anxiety, depression and chronic pain

He showed healthy young men who endured just a single night of four hours’ sleep lost 70 per cent of the natural killer cells circulating in their immune system.

You can well imagine the enfeebled state of your cancer-fighting armoury after a week of short sleep, let alone months or years.

A European study of almost 25,000 individuals demonstrated that sleeping six hours or less is associated with a 40 per cent increased risk of developing cancer, compared with people sleeping seven hours a night or more.

Stirred by the strength of accumulating evidence, Denmark became the first country to pay compensation to women who had developed breast cancer after years of night-shift work in government-sponsored jobs, such as nurses and air cabin crew.

FIRST-NIGHT JITTERS

If you take someone to an unfamiliar sleep environment such as a hotel, half of their brain sleeps a bit more lightly than the other, as if it is standing guard with a tad more vigilance due to the potentially less safe context that the conscious brain has registered while awake.

The more nights someone sleeps in the new location, the more similar the depth of sleep in each half of their brain, as they become accustomed to the environment and feel safer.

It is perhaps the reason why so many of us sleep so poorly the first night in a hotel room.

RETIRED, AND PLAIN TIRED

Sadly, the parts of our brain that ignite deep sleep at night are the same areas that degenerate earliest and most severely as we age. Ageing brains do not deteriorate uniformly. Instead, some regions start losing neurons much earlier and faster than others.

The areas that suffer the most dramatic deterioration with age are the ones that generate deep sleep — the middle-frontal regions seated above the bridge of your nose.

More is more: More than 750 scientific studies —often using professional and elite athletes — have investigated how bad sleep harms our physical performance

This type of deep sleep also plays a crucial role in cementing new memories. 

When my team and I looked at this — performing hundreds of brain scans and amassing almost a thousand hours of sleep recordings — we found the more severe an older person’s mid-frontal brain deterioration, the more dramatic their loss of deep sleep.

On average, older adults suffered a 70 per cent loss of memory-enhancing deep sleep, compared with young individuals.

Our tests found that older adults with the greatest loss of deep sleep showed the most catastrophic inability to remember new facts they had learnt the previous evening.

Older people also suffer from a shift in their body clock’s daily rhythm — their circadian timing. They commonly experience a regression in sleep timing, leading to earlier and earlier bedtimes.

The cause is an earlier evening release and peak of the sleep-inducing hormone melatonin as we get older.

Changes in circadian rhythms with ageing may appear harmless, but they can be the cause of numerous sleep problems.

Older adults often want to stay awake later into the evening so they can go to the theatre or cinema, socialise, read or watch television. But in doing so, they find themselves waking up on the couch or in a cinema seat, having inadvertently fallen asleep mid-evening; their new circadian rhythm left them no choice.

Yet what seems like an innocent doze has a damaging consequence. The early evening snooze will clear away the sleepy power of adenosine that had been steadily building throughout the day. Several hours later, when that older individual gets into bed, they may not have enough sleep pressure to drop off quickly, or stay asleep as easily.

WINNING WAYS IN THE BEDROOM 

If you don’t snooze, you lose. More than 750 scientific studies —often using professional and elite athletes — have investigated how bad sleep harms our physical performance.

The results show that if a competitor gets anything less than eight hours of sleep a night — and especially less than six hours — they become physically exhausted up to a third more quickly.

Likewise, their muscle strength diminishes, their lungs become less efficient and they can’t jump as high. Even their body’s ability to cool itself through sweating — a critical part of peak performance — is impaired by sleep loss.

On top of this is the problem caused by coaches who stoically have their athletes wake in the early hours of the morning to practise, foregoing their last two hours of a healthy eight hours’ rest.

Those last two hours of sleep are precisely the ones that many of us feel it is OK to cut short to jump-start our day.

However, my research has found that this late-morning phases of sleep is essential to help consolidate motor-skill memories, boosting next-day performance by 20 to 30 per cent. By forcing athletes to rise early, coaches may be innocently denying their charges of a game- or medal-winning performance advantage. 

SLEEPLESS AND HUNGRY 

Why do we lust after quick fixes of sugar and carbs when sleep-deprived? 

My research team has scanned healthy, average-weight people’s brains while they were picking items to eat from a range of healthy and unhealthy foods.

The volunteers did this both when they had enjoyed a full night’s sleep and after they had been sleep-deprived for a night. When sleep-deprived, the volunteers chose foods that contained, on average, 600 calories more than those they picked when properly rested.

Our brain scans showed regions in the prefrontal cortex required for thoughtful decisions had been silenced by a lack of sleep.

These impulse-control regions normally keep our food desires in check, making us reach for whole grains and leafy greens rather than doughnuts or pizza. In contrast, the more primal deep-brain structures that drive motivations and desire were amplified.

Matthew Walker is a professor of neuroscience and psychology and director of the Center for Human Sleep Science at the University of California, Berkeley.  

Why We Sleep: The New Science Of Sleep And Dreams, by Matthew Walker, is published by Allen Lane, £20. To order a copy for £16, visit mailbookshop.co.uk or call 0844 571 0640. 

P&P is free on orders over £15. Offer valid until September 26.